A file contains 4 billion integers, each of which is 4 bytes and memory is 1 GB. Write an algorithm: Find an integer not included in the file

An integer expressed in four bytes. A total of only 2 ^ 32 is approximately 4G.
For the sake of simplicity, we can assume that they are all unsigned integers.
Allocate MB memory. Each bit represents an integer, which can represent an integer of 4 bytes. The initial value is 0. The basic idea is to set the corresponding bit location to 1 for each number read. After processing the 40 Gb number, traverse the memory of MB to find a bit of 0, the integer corresponding to the output is not displayed.
Algorithm flow:
1) Allocate MB of memory Buf and initialize it to 0
2) unsigned int x = 0x1;
For each Int J in file
Buf = Buf | x <J;
End
(3) For (unsigned int I = 0; I <= 0 xffffffff; I ++)
If (! (BUF & x <I ))
{
Output (I );
Break;
}
The above is only for unsigned, and signed integers can be pushed accordingly.